#include <iostream>
#include <filesystem>
using namespace std;
namespace fs = std::filesystem;
using namespace filesystem;

int main()
{
    // 判断 a.txt 是否存在
    if (exists("a.txt"))
    {
        cout << "a.txt exists." << endl;
    }
    else
    {
        cout << "a.txt not exists." << endl;
    }

    if (fs::exists("a.txt"))
    {
        cout << "a.txt exists." << endl;
    }
    else
    {
        cout << "a.txt not exists." << endl;
    }
}
